Heli-borne snipers, four-layered security cordon around CWG venues were part of security plan unveiled by the government.

The security plan prepared for the event, which would see participation from around 8,500 athletes from 71 countries competing in 17 events, also envisages snipers on rooftops, commando hit teams and expert groups to tackle any chemical, biological, or nuclear attacks.

Unveiling the plan, Delhi Police Commissioner Y S Dadwal told reporters, "we will be looking at not only into securing the Games. Each and every aspect of security of the city has (also) been taken care of. We assure you a safe and secure Commonwealth Games".

According to the plan, the Games venues, Games Village, practice areas and parking lots as also the Indira Gandhi International Airport where athletes will arrive will have a four-layered security cordon.

Special Commissioner (Administration) Neeraj Kumar said there will be surveillance from the skies with the help of the Air Force. "There will also be the deployment of heli-borne assault teams to thwart any terror strikes," he said.

He said the venues, village and hotels will be "locked down" a week before the start of the event after extensive anti-sabotage security checks.

"For easy travel of athletes and officials, an exclusive lane will be provided," Dadwal said.

Elaborating on the security at venues, Kumar said the 12 venues will have "outer, middle, inner and exclusive" security zones.

At the outer cordon, he said, the traffic will be stopped and access controlled. At the middle cordon, securitymen will channelise the spectators to their designated seats while in the inner cordon, the barcode reading of tickets to see their originality will take place and spectators' photos captured.

Mobile Quick Reaction teams will be deployed on the outer perimeter of the venues besides keeping a close watch through CCTV surveillance, Kumar said.

"We are closely working with central intelligence agencies. The Air Force will be surveying the airspace. We will have heli-borne snipers patrolling the skies," he said.

At the centre would be an exclusion zone which is in the 30 metre radius of the stadium, he said adding spectators and others will have to go through Door-Frame Metal Detectors and X-Ray scanning besides manual searching.

The Games village will also have a similar elaborate security arrangement. The boundary of the village will have a three metre high perimeter wall, a 1.5 metre high iron grill on top of it, mobile QRTs and CCTV surveillance system.

"The Games village will have a Chemical, Biological, Radio-active, Nuclear Explosives response team deployed there.

The airspace will be kept secure by the Air Force while heli-borne assault teams will hover in the skies," Kumar said.

Elaborate arrangements will also be made for the entry for athletes and vehicles into the village. After entering the village following a thorough check, the athletes can freely move around the residential and dining halls.

For vehicles, the drivers will have to pass through radio frequency identity checking where the number plates are checked to see whether they are authorised to enter the place.

"There is a boom barrier and it will be opened only after the vehicle clears the radio frequency checking. But if somebody tries to enter forcefully, there will be a tyre-killer and even if the vehicle clears it, the road blocker will block the passage of the vehicle," Kumar said.

At the hotels, there will be "robust" security. "There will be watch towers, CCTV surveillance and access control. We will screen the work force. A separate block will be earmarked for Games officials and family of athletes. They will be segregated from the other clients of the hotel."

A dedicated parking space will also be earmarked at the hotels for those guests related to Games.

"All food prepared and served for Games guests in hotels will be sorted by security personnel and tasted by food experts," he said.

For the road events -- marathon, cycling and walkathon -- special traffic arrangements have been made. "All buildings on the route will be secured and sanitised. The telephone boxes and electric boxes will also be sanitised," Kumar said.

QRTs, Commando hit teams and heli-borne assault teams will give security to those athletes participating in the road events, Kumar said.

With large number of athletes, officials and tourists reaching the city for the Games, security at and around the Indira Gandhi International Airport will also be augmented.

"The perimeter of the airport has already been secured.

Access control will be further strengthened," Kumar said adding tight security arrangements have been made for their journey from the airport to Games village as well as hotels.

Keeping in mind the attack on Sri Lankan cricketers earlier this year in Pakistan, Kumar said the route network for their journey has been identified and surveyed.

"We have alternate routes also in case of an emergency.

There will be some surprise element in our strategy," he said.

On the route between airport and Games Village, there will be 15 intervention bases which will be at a distance of two kilometres each.

Anti-sabotage teams, commando hit teams and snipers at rooftop are some of the other components of security plan for the safe journey of the athletes and other officials.

Police have also drawn up an extensive plan for the vehicles being used for the Games. "All the vehicles will be parked at the designated parking slots at night. They will be thoroughly checked before they are taken next day," he said.